Create FibonacciNumber.cpp

[CoderAayush2104]

Fixes #826

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[CoderAayush2104]

The code is incorrect for the input N = 10 it should be 55 and not 34. It is a minor bug fix it. If you cannot then tell us we will help you.

Sir but for n = 10 answer is 34 as the series starts from 0. I have also attached the photo of the series.Please review my pull request.

[CoderAayush2104]

Please merge my request.